Global Distribution of Fe K alpha Lines in the Galactic Center Region Observed with the Suzaku Satellite

TL;DR

This study maps the distribution of Fe K alpha lines in the Galactic Center using Suzaku, revealing differences in the origin of diffuse X-ray emissions between the Galactic Center and ridge regions, and suggesting a possible diffuse plasma origin.

Contribution

First detailed spatial profile analysis of Fe K alpha lines in the Galactic Center, comparing with stellar mass models and discussing origins of the diffuse X-ray emission.

Findings

Fe K alpha lines are spatially resolved with ~0.1 degree resolution.

Fe XXV K alpha profile matches stellar mass distribution in the Galactic ridge.

Excess Fe XXV K alpha emission in the Galactic Center suggests a different origin.

Abstract

We have surveyed spatial profiles of the Fe K$\alpha$ lines in the Galactic center diffuse X-rays (GCDX), including the transient region from the GCDX to the Galactic ridge X-ray emission (GRXE), with the Suzaku satellite. We resolved Fe K$\alpha$ line complex into three lines of Fe \emissiontype{I}, Fe \emissiontype{XXV} and Fe \emissiontype{XXVI} K$\alpha$, and obtained their spatial intensity profiles with the resolution of $\sim \timeform{0D.1}$. We compared the Fe \emissiontype{XXV} K$\alpha$ profile with a stellar mass distribution (SMD) model made from near infrared observations. The intensity profile of Fe \emissiontype{XXV} K$\alpha$ is nicely fitted with the SMD model in the GRXE region, while that in the GCDX region shows $3.8\pm0.3$ $(\timeform{0D.2}<|l|<\timeform{1D.5})$ or $19\pm6$ $(|l|<\timeform{0D.2})$ times excess over the best-fit SMD model in the GRXE region. Thus Fe \emissiontype{XXV} K$\alpha$ in the GCDX is hardly explained by the same origin of the GRXE. In the case of point source origin, a new population with the extremely strong Fe \emissiontype{XXV} K$\alpha$ line is required. An alternative possibility is that the majority of the GCDX is truly diffuse optically thin thermal plasma.